Long-Range σ−π Interactions in Tetrahydro-<i>4H</i>-thiopyran End-Capped Oligo(cyclohexylidenes). Photo-Electron Spectroscopy, ab Initio SCF MO Calculations, and Natural Bond Orbital Analyses
作者:Albert W. Marsman、Remco W. A. Havenith、Sabine Bethke、Leonardus W. Jenneskens、Rolf Gleiter、Joop H. van Lenthe、Martin Lutz、Anthony L. Spek
DOI:10.1021/jo000199y
日期:2000.7.1
alpha- and omega-end positions the pi-type sulfur lone pair bands [Lppi(S)] split significantly by deltaIvj approximately 0.3 to 0.4 eV (delta-epsilonj approximately 0.3 to 0.4 eV), i.e. sigma-pi interactions over distances of ca. 8 and 12 A, respectively, occur. The magnitude of the interactions and the observed splittings are independent of the anti and syn conformations of the oligo(cyclohexylidene) hydrocarbon
通过He(I)光电子能谱(PES)和从头算RHF / 6-31G *计算,确定了在四氢4H-硫代吡喃末端封端的寡核苷酸(环己叉基)中的远距离sigma-pi相互作用。使用Koopmans定理(Iv,j = -epsilonj)并通过与相关参考化合物的电离作用相关联,分配最高占据分子轨道(MO's)的垂直电离能Ivj。实验(PES)和理论(RHF / 6-31G *)结果吻合良好。对于含有两个非共轭π键分裂δIv的三环己叉基衍生物,π带的j在约0.5至0.7eV的范围内(δε约0.6至0.9eV)。对于在其α和ω末端位置包含两个硫原子的双环和亚环己基化合物,pi型硫孤对带[Lppi(S)]的相差约为0.3-0.4 eV,δ-ε约为0.3-0.4 eV。 0.4 eV),即s距离上的sigma-pi相互作用。分别出现8和12A。相互作用的大小和观察到的分裂与寡(环己叉)烃骨架的反构象和同构象无关。RHF